This invention relates generally to the assembly of printed circuit board assemblies (PCBAs) and electronic components, and more particularly to a tape feeder device with splicing capabilities for reliably conveying parts to a pickup location for soldering to a substrate using a pick and place assembly machine.
The present invention is a spliceable tape feeder device for reliably conveying parts to a pickup location for soldering or similar attachment to a substrate using a pick and place assembly machine. Component carrier tape used in tape feeding equipment typically comprises a plastic or similar strip having depressions at regular intervals containing the part to be mounted on the substrate and a second, plastic cover strip covering the depressions to retain the parts in the depressions during transport and use. Such tapes are generally of a limited length that is determined by the size of the components and the capacity of the fed reel that supplies the feeder. However, this invention relates to a tape feeder device that can feed such carrier tapes in a variety of formats, wherein the feeder incorporates certain functions and features that enable splicing of the feeder tape, where the need to remove the feeder from the pick-and-place system is eliminated.
The preferred method for the automated construction of circuit boards requires the use of high speed pick and place machines that pick components from a pickup location and place them at required locations on a printed circuit board for attachment. Pick and place machines rely on feeding mechanisms or feeders to reliably feed the required parts to the expected pickup location. It is well-known in the industry to package small electronic parts such as integrated circuit chips in a component carrier tape that is characterized by a flexible strip with depressions formed at regular intervals along its length. A part is disposed in each depression and secured by a cover strip that is adhered along its edges to the carrier tape. Parts that are packaged in a carrier tape require the cover strip be peeled away from the carrier tape and that the carrier tape be advanced to bring the next part to the pickup location. Normally, the cover tape is peeled back from the carrier tape at a point just prior to the pick location as the tape is advanced. In systems that are intended to enable spliceable feeding, the handling of the cover tape, after being peeled back from the carrier tape, is an important consideration. More specifically, it is important that such a feeder provides means for the storage or disposal of cover tape from a plurality of reels of carrier tape containing components.
Electronic parts are packaged in carrier tapes in a variety of formats, depending on the size of the part being delivered. In particular, carrier tapes are available in varying widths and pitches. The width is the distance from edge to edge perpendicular to the length of the tape. Widths common in the industry are 8 mm, 12 mm, 16 mm, 24 mm and larger. The pitch of a carrier tape is the distance from one depression (e.g. lead edge) to the next (lead edge) along the length of the tape. Tapes are wound on reels and transported to the manufacturing facility. It is obvious that the part manufacturer and user will desire to use the smallest pitch tape permissible for the size of the electronic component in order to reduce the length of the tape required, thereby reducing the size and/or number of reels for the required task. Additionally, the pocket is required to be only slightly larger than the component in order to control the orientation of the component within the pocket.
In accordance with the present invention, there is provided a carrier tape feeder, comprising: a carrier tape reel support for supporting carrier tape, wherein said carrier tape reel support is extendible along a longitudinal axis of the tape feeder so as to provide access to the support during reloading of the feeder; a guide for guiding said carrier tape from a carrier tape reel to a tape guide at a pick location; and a carrier tape drive mechanism for engaging feed-holes regularly spaced along the length of carrier tape and advancing said carrier tape through said tape guide.
In accordance with another aspect of the present invention, there is provided a cover tape take-up reel, comprising: an inner flange having a tapered inner hub extending from the center thereof; an outer flange having a tapered outer hub extending from the center thereof toward the inner hub; a locking mechanism for interconnecting said inner and outer flanges wherein when the flanges are interconnected they are maintained in a generally parallel relationship, and where the inner and outer hubs, in an adjacent relationship, provide a hub suitable for winding a cover tape thereon; and where cover tape removal is facilitated by separating the outer plate from the fixed inner plate resulting in a reduced hub diameter due to the tapered outer hub.
In accordance with yet another aspect of the present invention, there is provided a system for determining the state of fill of a cover-tape take-up reel, comprising: a cover tape take-up reel disposed subsequent to a peel edge for receiving a cover tape peeled from an advancing carrier tape; take-up reel drive means for rotating said reel in association with the advancement of a carrier tape; a spring-loaded peel arm having at least one roller disposed thereon, wherein said roller is disposed between the peel edge and the take-up reel and where the cover tape is wound at least partially about the roller such that advancement of the take-up reel results in the movement of the peel arm about a pivot point; a sensor for sensing the rotation of the peel arm; a take-up reel drive controller for initiating the rotation of the take-up reel at the time of advancement of the cover tape; and a calculator for estimating the state of fill of the take-up reel as a function of the relationship between the initiation of the rotation of the take-up reel and the signal produced by said sensor.
One aspect of the invention is based on the discovery that with various improvements it is possible to produce a tape feeder that will overcome cover-tape disposal problems and will enable on-the-fly splicing and/or changing of tapes without removal from the pick and place machinery. Moreover, the various aspects of the invention, including a split-hub take-up reel, sensing of take-up reel state of fill, and an extendible carrier tape support, all facilitate the improved performance of a spliceable tape feeder. Combined with sensing of take-up reel state of fill and the split-hub reel design, the extendible carrier tape support enables the splicing of a limited number of component tapes before the feeder must be removed from the assembly system.
This aspect is further based on the discovery of techniques that facilitate the use of a single take-up reel for multiple component carrier tape reels, including the sensing of the state of fill of the take-up reel. The cover tape disposal aspect of the present invention is accomplished using a split-hub take-up reel, wherein the hub includes a keyed or locking hub to lock inner and outer hubs together, along with a tapered flange on each so as to facilitate removal when the hubs are separated. The take-up reel fill status aspect is accomplished using a peel arm and tension spring, wherein the position of the peel arm after, advance of the take-up reel, is used to accurately estimate the level to which the take-up reel has been filled. The extendible carrier tape support is preferably implemented by a slide-mounted support that, upon release of an associated latch, allows the support to be shifted relative to the feeder body and enables a user to access the rear of the feeder to install a new carrier tape without removing the feeder or interfering with adjacent feeders.
The techniques described above are advantageous because they are flexible and one or more of the techniques can be adapted to any of a number of tape feeding systems. The techniques of the invention are advantageous because they provide for changing of a component tape reel without the need to interrupt the assembly system. In addition, some of the techniques described herein can be used separately in certain situations so as to achieve similar functionality. As a result of the inventions described herein, tape feeders with improved flexibility and functionality may be produced.